Telegraph system



Dec. 20, i1938. M. L. GREENE ET A1.

TELEGRAPH 4SYSTEM Filed Jan. 1957 Ell ML- cRff/VE mLn/foAas/e.

A TTORNE V Patented Dec. 20, 1938 UNITED s-'mrlazsI PATENT OFFICETELEGRAPH SYSTEM.

ofNew York Application January 29, 1937, Serial. No.- 123,064

2 Claims.

This inventionr relates to a telegraph system, and more particularly toa system for transmit-v ting telegraph signal pulses over along.telegraph.

proved telegraph circuits and. arrangementsy which require lessadjustment and maintenance at the outlying station. Y

Another object ofthis invention is to vprovide a telegraph system whichrequires no changes in the` adjustments of the apparatus at the outlyingstation With changes in the leakage resistance of the line due toweather changes.

Stillanother object of this invention relates to a telegraph system inwhich the polarized receiving relays are p-rovided at each end of theline; These receiving relays do not require any mechanical or electricalbias under. normalor dry Weather conditions.

These and otherv objects and features of the invention can be morereadily understood from `the iollowingf description when read withreference to the attached drawinginwhich isshovvn graph leg of acomposite toll line, andinclude.

the usual terminal and intermediatev com-.- posite sets. Line I6 mayalso be either an open wire line or a cable circuit, ora portion ofitmay include open wire lines and other portions cable conductors.

The usual noise suppression filter units may also be included. Thesenoise' suppression units.

' have not been shown becauseA they operate in their usual and normalmanner which is well understood so that further description of themwould only needlessly complicate the description and tend to obscurethis invention.

At the outlying station B, the receiving polarized relay Il is connecteddirectly in series with line IB. The line circuit is then connected tothe its marking contact. Polarized relay. Il operates This telegraphchannel may be an.

receivingldevice l2. Receiving device l2 may be of any suitable type,`as for example a telegraph sounder or printing magnet of ateletypewriter.

'I'he transmitting relay i3 is controlled from the contacts 30 of thetransmitting device at the outlying station B. Transmitting device 3Gmay be of any suitable type, as for example atelcgraph key, contacts ofa tape transmitter or of a teletypewriter keyboard. The current iiowingthrough the upper or biasing winding of the transmitting'relay i3 is insuch a direction as to tend to move the armature to the spacing contact.The current iiowing through'the lower winding of sending` relay i3 whenthe transmitting contacts Sill are closed, tends to move the armatureofl relay i3 to its marking contact. This current owing through thelower winding of sending relay |3` causes a magnetic eiiect upon therelay armature which overcomes the magnetic effect of the upper biasingwinding. In the preferred embodiment both windings or relay i3 are thesaine while the' current throughthe lower winding whencontacts 3d areclosed is twice the current Iiowing through the upper winding: Thiscausesv the relay to move to and remain upon its marking contact so longas transmitting contacts 3Q., remain closed, However, when contacts 3i!are vopen in accordance with the signal pulses to be transmitted, thecurrent flowing through the lower'winding of the sending relay I3 fallsto zero at which time the current owing through the upper or biasingwinding causes the armature to Amove to vits spacing position andconnect the postive 13D-volt. battery to the line circuit. Thus, thesending relay I3 connects ground and positive 130volts to line-lil`through the Winding of receiving. relay l l in accordance with thesignal'ipulses. transmitted from station B.

At station A, line lll is connected to the armature ci polarized relay I6. Positive 65 volts is connected to the marking contact of relay I6through the lower winding of the polarized receiving relay i3. Negative65 volts is connected to the spacing Contact of relay i6. Receivingrelay i831 is provided with an upper winding which is normallyshort-circuited by break relay Il. Relays i, Il and |8-are shownconnected to a local subscribers line circuit.

It is to be understood that they may comprise relays of any suitableline circuit or repeater, including carrier current repeaters, duplexrepeaters or single line repeaters. As shown, receiving relaylretransmitssignals received from line lil to ther subscribersstation2'4- over line 25'in a mannerwell .understood-in the priorart and neednot be described herein. In addition, polarized relay I6 repeats thesignal impulses received from subscribers station 24 in the usual mannerso that this also need not be described in detail. However, the breakrelay Il provides a circuit for controlling the locking of upper windingof relay I8. When the attendant at the subscribers station 24 transmitsa break signal during the time signal station 24 transmits a spacingsignal it will cause the sending relay I5 and the break relay Il to moveto their spacing positions if the armature of relay IS is in its markingposition. When break relay Il leaves its marking contact it removes ashort circuit from the upper or locking winding of the receiving relayI3, which causes current to flow through the locking winding of relayI8. This current is in such a direction as to maintain this relay on itsmarking contact. This insures the proper transmission of the spacingsignal to the lines Il) by preventing the armature of relay I6 fromleaving the spacing Contact. Relay Il also functions in the above mannerduring long spacing or break signals transmitted from station 24 andinsures the proper transmission o these signals to line I@ independentlyof any impulses which may be transmitted from station B over line i6.This insures the reception of the break signal at station B.

During the time signal pulses are being transmitted from subscribersstation 25, positive and negative potentials or 65 volts are connectedto line I by the sending relay I@ in accordance with the pulsestransmitted. During this time the transmitting contacts 30 at station Bnormally vremain closed so that the line circuit Ill is normallyconnected to ground I5. Under these conditions, positive and negativepotentials connected to line I0 by relay I6 at station A cause positiveand negative currents to flow over line lil and through relay I I toground I .at station B. Since the positive and negative potentialsconnected to line I0 at station A are substantially equal and opposite,they will cause substantially equal and opposite currents to flow inline ID. These currents operate receiving polarized relay l l equally inboth directions, in the absence of any bias, as shown and described. Inaddition any leakage current will aiect both the positive and negativecurrent received by relay Ii at station B in substantially the samemanner so that the adjustment of this relay need not be altered tocompensate for changes in the leakage resistance of the line. Thus, thebias of the signals received at station B is substantially independentof any leakage resistance of the line.

The term bias as applied to the received signals indicates a lengtheningof one signal impulse and the shortening of another signal impulse; forexample, marking bias means that the marking signal impulses arelengthened while the spacing signal impulses are correspondinglyshortened, Whereas spacing bias means that the spacing signal impulsesare lengthened and the marking signal impulses are correspondinglyshortened. Thus the greater the bias of the signals, the lesssatisfactory they are for operating telegraph apparatus and relays,while the less bias, the better the quality of the signal impulses.

The common cause of this lengthening and shortening of the varioussignals is that marking and spacing currents are unequal; for example,for marking bias, the marking current is greater than the spacingwhereas for spacing bias, the spacing current is greater than themarking current. These unequal currents cause the receiving relay torespond differently to the two conditions and thus add bias to thesignal pulses. However, as pointed out above, the receiving relay II atstation B receives substantially equal positive and negative currentsrepresenting the marking and spacing signaling conditions independentlyof the line leakage. Consequently, the receiving relay I I does notintroduce any bias in the received signals and does not require anychanges in the adjustment of the relay to compensate for changes of theline leakage.

The terms marking and spacing as used in this specication diierentiatetwo line or signaling conditions transmitted between the telegraphstations. The term marking is used to designate the line or signalingcondition employed during the time no signal impulses are beingtransmitted, but the system is energized ready to transmit signalimpulses. The term spacing designates the other signal or linecondition.

When a spacing impulse is transmitted from station B the armature of thesending relay I3 at station B connects a potential of positive 130 voltsto line lil. At this time the sending relay I6 at station A is normallymaintained on its marking contact so that positive 65 volts is connectedto line I at station A. 130-volt positive potential connected to line I0at station B is substantially twice as great as the 65-volt positivepotential connected to the line at station A, vand consequently causessubstantially equal but opposite current to ow over line I0. Thiscurrent is substantially the same as flows over line I0 during the timethe armature of the sending relay I3 at station B is in its markingposition and the armature of relay I8 at station A is in its spacingposition. This reversed current causes the armature of the receivingrelay I I at station B to move to its spacing position, and thus repeatthe transmitted signals to the receiving device I2 to record a homecopy. Since during the time signals are being transmitted from stationB, the sending relay I6 at station A is maintained on its markingcontact, the receiving relay I8 at station A will follow the currentreversals transmitted over line I() and repeat the signal impulses tosubscribers station 24 over line 25.

As pointed out above, with the potential connected to the spacingcontact of relay I3 at station B substantially twice the potentialconnected to the marking contact of relay I6 at station A, the markingand spacing currents flowing in line Iii during the transmission ofsignal impulses from station B will be substantially equal in magnitudebut opposite in polarity. Consequently, no mechanical or electrical biasis required for the receiving relay I8 at station A under thiscondition.

The foregoing description describes one specific embodiment of thisinvention, the scope of which is set forth in the following claims.

What is claimed is:

l. In a telegraph system, a line, a polarized relay associated with eachof the ends of said line and responsive to reversals of currentthereover, a transmitting device associated with each end of said line,each device having a spacing and a marking contact, a rst source ofcurrent or" one polarity and one potential associated with the spacingcontact oi the first of said devices, a second source of current oropposite polarity and different potential associated with the spacingcontact of the second of said devices, a third source of current equalin potential, but opposite in polarity to said rst source associatedwith the marking contact of said rst device through the operatingWinding of the relay with Which said device is associated, and a sourceof ground potential associated with the marking contact of said seconddevice, the relative potentials of said sources being such that the flowof current in each direction over said line is substantially equal whenthe marking contact of either device is held closed and the other deviceis operated to close either its spacing or marking contact.

2. In a telegraph system, a line, a polarized relay associated with eachof the ends of said line and responsive to reversals of currentthereover, a transmitting device associated with each of said relays,each device having a spacing and .a marking contact, sources of currentof equal potential and of opposite polarities asscciated with thespacing and marking contacts of one of said devices, one of said sourcesbeing associated with one of said contacts through the operating windingof the relay with which said device is associated, a source of currentor" different potential associated With the spacing contact of the otherof said devices, and a source of ground potential associated with themarking contact of said other of said devices.

MONTE LEE GREENE.

WILLIAM LOCKWOOD RHOADS, SR.

